The only documentation currently available is the AvalonDock samples that can be downloaded from codeplex. http://avalondock.codeplex.com/releases
Beyond this, the intellisense is a helpful guide.
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The error you are seeing for 'DockingManager' is misleading as it still exists in 2.0. The following may help you get rid of those. Additionally, intellisense will begin to work once this is resolved.
Bad things happen with files downloaded from the internet. They have an attribute on them that leads to limited access. You have to manually remove this attribute in order for the XAML to stop fussing.
In windows explorer, right-click the file, choose properties, then click the 'Unblock' button. Do this for every individual file you are using that was downloaded from the internet. Be sure to rebuild the project to replace the blocked copy in the bin folder as well.
As a side note, I am able to still run the project whenever this is the issue. Only the XAML editor thinks that there is a problem.
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In 2.0, everything is nested in layout controls. All of your panes are either anchorable or document style. Here is a quick example to get you going.
Define your namespace
xmlns:ad="http://avalondock.codeplex.com"
Build your DockingManager
<ad:DockingManager x:Name="dockManager">
<ad:LayoutRoot>
<ad:LayoutPanel Orientation="Horizontal">
<ad:LayoutPanel Orientation="Vertical">
<ad:LayoutPanel Orientation="Horizontal">
<ad:LayoutDocumentPaneGroup x:Name="leftDocumentGroup">
<ad:LayoutDocumentPane>
<ad:LayoutDocument Title="Left Doc"></ad:LayoutDocument>
</ad:LayoutDocumentPane>
</ad:LayoutDocumentPaneGroup>
<ad:LayoutDocumentPaneGroup x:Name="rightDocumentGroup">
<ad:LayoutDocumentPane>
<ad:LayoutDocument Title="Right Doc"></ad:LayoutDocument>
</ad:LayoutDocumentPane>
</ad:LayoutDocumentPaneGroup>
</ad:LayoutPanel>
<ad:LayoutAnchorablePaneGroup x:Name="bottomAnchorableGroup">
<ad:LayoutAnchorablePane>
<ad:LayoutAnchorable Title="Bottom Anch"></ad:LayoutAnchorable>
</ad:LayoutAnchorablePane>
</ad:LayoutAnchorablePaneGroup>
</ad:LayoutPanel>
<ad:LayoutAnchorablePaneGroup x:Name="rightAnchorableGroup">
<ad:LayoutAnchorablePane>
<ad:LayoutAnchorable Title="Right Anch"></ad:LayoutAnchorable>
</ad:LayoutAnchorablePane>
</ad:LayoutAnchorablePaneGroup>
</ad:LayoutPanel>
</ad:LayoutRoot>
</ad:DockingManager>